On the Arasaki Coast of the Miura Peninsula in Kanagawa Prefecture, Japan, there are striped strata with a crisp pattern of black and white. Two different colors of volcanic ash fall alternately to form such a formation. The whitish layer is a rhyolitic volcanic ash layer. The grain size is finer than sand and is classified as silt. On the other hand, the black layer is a basaltic volcanic ash layer, which has coarser grain size than the white layer and is classified as sand to gravel. Since there are more gravels in the black layer, it may be more appropriate to call it a scoria layer rather than a volcanic ash layer. The black layer was more resistant to wave erosion than the white layer, and the black areas were convex.
